import launch
import launch.event_handlers
import launch_ros
from ament_index_python.packages import get_package_share_directory
import launch_ros.parameter_descriptions
from launch.launch_description_sources import PythonLaunchDescriptionSource

def generate_launch_description():
    # 机器人模型名称
    robot_name_in_model = 'wheel_legged_robot'
    # 获取默认路径
    urdf_package_path = get_package_share_directory('wheel_legged_robot_description')
    default_model_path = urdf_package_path + '/urdf/wheel_legged_robot.urdf'
    default_gazebo_world_path = urdf_package_path + '/world/custom_room.world'

    # 声明一个urdf参数方便修改
    action_declare_arg_mode_path = launch.actions.DeclareLaunchArgument(
        name='model_path', default_value=str(default_model_path),
        description='加载的模型URDF文件的绝对路径'
    )

    # gui参数
    action_declare_gui_arg = launch.actions.DeclareLaunchArgument(name='gui', default_value='true', choices=['true', 'false'],
                                    description='Flag to enable joint_state_publisher_gui')

    # 通过文件路径获取内容，并转换成参数值对象，传递给robot_state_publihser
    robot_description = launch_ros.parameter_descriptions.ParameterValue(
        launch.substitutions.Command(
            ['xacro ',launch.substitutions.LaunchConfiguration('model_path')]
        ),
        value_type=str
    )

    # 状态发布节点
    action_robot_state_publisher = launch_ros.actions.Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        parameters=[{'robot_description': robot_description}]
    )

    # 通过IncludeLaunchDescription包含另外一个launch文件，来加载world环境
    action_launch_gazebo = launch.actions.IncludeLaunchDescription(
        PythonLaunchDescriptionSource([get_package_share_directory('gazebo_ros'),'/launch','/gazebo.launch.py']),
        launch_arguments=[('world',default_gazebo_world_path),('verbose','true')]
    )

    # gazebo加载节点
    action_gazebo_start = launch_ros.actions.Node(
        package='gazebo_ros',
        executable='spawn_entity.py',
        arguments=['-topic','/robot_description',
                   '-entity',robot_name_in_model,]
    )


    return launch.LaunchDescription([
        action_declare_arg_mode_path,
        action_declare_gui_arg,
        action_robot_state_publisher,
        action_launch_gazebo,
        action_gazebo_start,
    ])